1. Field of the Invention
The present invention relates, in general, to a plasma display apparatus and, more particularly, to a sustain driving apparatus that supplies a sustain signal to a plasma display panel.
2. Background of the Related Art
A plasma display panel (hereinafter, referred to as “PDP”) is adapted to display an image by exciting phosphors by vacuum ultraviolet rays (VUV) generated during the discharge of a mixed inert gas.
The PDP is advantageous in that it can be made large and thin and can be easily fabricated due to its simple structure, and also has high luminance and emission efficiency compared to other flat display devices. More particularly, an AC surface discharge type three-electrode PDP has the advantages of a lower driving voltage and a longer lifespan since wall charges accumulated on a surface during a discharge protect electrodes from sputtering generated by the discharge.
To implement gray levels of an image, the PDP is driven with one frame being time-divided into a reset period for initializing the entire cells, an address period for selecting cells, and a sustain period for generating a display discharge on selected cells.
That is, one frame period is divided into several subfields having a different number of sustain discharges depending on luminance weights. Each subfield is divided into a reset period, an address period, and a sustain period.
FIG. 1 is a block diagram of a general PDP driving apparatus. The driving apparatus includes a sustain driver 3, an address driver 4, and a scan driver 5.
A panel 1 includes scan electrodes Y1 to Yn and sustain electrodes Z1 to Zn, which are alternately disposed horizontally, and address electrodes X1 to Xm disposed vertically. The scan electrodes Y1 to Yn are generally used to scan the screen and sustain a discharge, the sustain electrodes Z1 to Zn are generally used to sustain a discharge, and the address electrodes X1 to Xm are generally used to input data.
The scan driver 5 supplies a sustain signal for sustaining a discharge of a cell, an erase signal for stopping a discharge of a discharged cell, a scan signal synchronized with a video data signal applied to the address electrodes X1 to Xm, and so on to the respective scan electrodes Y1 to Yn. Furthermore, the sustain driver 3 commonly supplies a sustain signal, etc. to the sustain electrodes Z1 to Zn, and the address driver 4 supplies the data signal to each of the address electrodes X1 to Xm.
The sustain discharge of the AC surface discharge type PDP driven as described above requires a high voltage. Therefore, an energy recovery apparatus that recovers a voltage between the scan electrode Y and the sustain electrode Z and supplies the recovered voltage as a driving voltage of a next discharge is used.
FIG. 2 is a circuit diagram of a general sustain driving apparatus including the energy recovery apparatus. The sustain driving apparatus includes an energy recovery unit 10 and a sustain driver 20.
The energy recovery unit 10 includes a source capacitor Cs, an inductor L, a first switch Q1 for supplying energy stored in the source capacitor Cs to a panel, and a second switch Q2 for recovering energy from the panel.
The sustain driver 20 includes a third switch Q3 for applying a sustain voltage Vs to the panel, and a fourth switch Q4 for dropping a voltage of the panel to a ground voltage GND.
It is required that when the sustain voltage Vs is applied to the panel, only the third switch Q3 be turned on, and when the ground voltage GND is applied to the panel, only the fourth switch Q4 be turned on. However, the third and fourth switches Q3 and Q4 may be turned on or off at the same time, or when the sustain voltage Vs is applied to the panel, the fourth switch Q4 may be turned on or when the ground voltage GND is applied to the panel, the third switch Q3 may be turned on, due to the error of the PDP driving apparatus, and/or so on. If such error occurs, the lifespan of a product is shortened due to the short since the first switches Q3 and Q4 are damaged. Furthermore, a problem arises because severe noise is generated.